Group roosting in the Grey-and-Buff Woodpecker Hemicircus concretus involving large numbers of shallow cavities

LAMMERTINK, MARTJAN

Forktail

Oriental Bird Club

Lugar: Sandy; Año: 2011 vol. 27 p. 78 - 82

0950-1746

The Grey-and-buff Woodpecker Hemicircus concretus is a small, short-tailed picid endemic to the Sundaic region, and one of two species in the genus Hemicircus which is sister to all other genera in the true woodpeckers (Picinae). I report the unusual roosting behaviour of Greyand-buff Woodpeckers observed at two roost sites in Kalimantan, Indonesian Borneo. Stable groups of three and four woodpeckers roosted individually in nearby cavities, with respectively 34 and 17 cavities per group, the adult males frequently working on excavation of additional cavities. The cavities were stacked above one another in series of up to 18 in one branch, and were clustered in adjacent dead branches or dead trees. Individual woodpeckers typically switched cavities within a cluster every night. The cavities were only about 2.5 cm deep below the entrance, and the woodpeckers roosted on the floors of these shallow cavities. In contrast, other woodpecker species typically sleep vertically against the wall of a deep cavity that is often an old nest cavity, rarely roost socially, have only a small number of roost cavities, and use the same cavity during prolonged series of nights. I speculate that Grey-and-buff Woodpeckers (1) roost on cavity floors because they are unable to prop themselves with their short tails against vertical cavity walls, (2) mitigate elevated predation risk in shallow cavities by roosting in groups, and (3) make shallow cavities to discourage cavity usurpers. Large numbers of cavities combined with frequent cavityswitching, may allow evasion of predators and of feather and skin parasites.